(CBS News) It's common knowledge that heart disease risk can be raised by smoking, obesity and your family history. Now, a new study adds to the list that your very own blood type might increase risk for future heart problems.

Harvard researchers have found that people with blood types A, B or AB have a higher risk for coronary heart disease than people with blood type O. People with the rarest blood type, AB, were found to have the greatest risk.

"While people cannot change their blood type, our findings may help physicians better understand who is at risk for developing heart disease," Study author Dr. Lu Qi, assistant professor in the department of nutrition at the Harvard School of Public Health in Boston, said in an American Heart Association press release.

For the study, researchers pooled data from two long-running U.S. studies that tracked 89,500 adults between the ages of 30 and 75 for 20 years or more. Researchers ruled out other heart-disease risk factors including the study participants' diet, age, body mass index (BMI), gender, race, smoking status, menopause status and medical history, to determine what role blood type had on heart disease risk in the general population.

The researchers found that people with type AB blood - found in only 7 percent of the U.S. population - were 23 percent more likely to develop heart disease. Those with type B blood had an 11 percent increased risk, followed by those with type A who had a 5 percent risk.

The lowest risk was seen for people with type O blood, which is most common and found in about 43 percent of Americans.

The findings were published online August 14 in the AHA's journal, Arteriosclerosis, Thrombosis and Vascular Biology

It's good to know your blood type the same way you should know your cholesterol or blood pressure numbers," said Qi. "If you know you're at higher risk, you can reduce the risk by adopting a healthier lifestyle, such as eating right, exercising and not smoking."

What explains the link between blood type and heart risk?

Qi said blood type is "very complicated" so the study did not examine the biological processes behind blood type and heart disease risk, but say multiple mechanisms may be at play.

But Qi used the example that knowing your blood type could lead to better treatments, if a person with type A blood would perhaps fare better if they decreased their daily cholesterol intake. Other study limitations included the participants were primarily white and it's not clear if the findings would translate to other races or ethnicities.

"It would be interesting to study whether people with different blood types respond differently to lifestyle intervention, such as diet," Qi said, noting that further analysis is needed.

Commenting on the research, Dr. Richard A. Stein, director of the exercise and nutrition program at NYU's Center for Prevention of Cardiovascular Disease told WebMD, "I actually don't know the blood types of any of my patients, and I would imagine that most cardiologists will tell you the same thing." He added, "Maybe this will prove to be useful in our assessments of how aggressively to treat patients, but we aren't there yet."

"Most of things that are this modest, most of the time they don't meaningfully change how you'd think about your risk overall," added Dr. Amit Khera, director of the Preventive Cardiology Program at the University of Texas Southwestern Medical Center in Dallas, to the Associated Press. "This shouldn't cause much alarm for most of the population," he added.

According to the American Red Cross, there are eight different blood types - A+, A-, B+, B-, O+, O-, AB+, AB - that are determined by the presence of immune-triggering antigens in the blood. That means if a person has blood type A and is given a transfusion from type B, that person's immune system might attack the transfused blood. Like eye color, the Red Cross says blood type is inherited genetically from a person's parents.

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